Passengers looking for a cheaper flight may have to watch out for extra fees on what used to be considered basic amenities. In exchange for lower ticket costs, some airlines are now charging for previously-included food and drinks, specific seat selection, and even carry-on bags.

The Associated Press reported an increase in fee-dependent airlines, after Denver-based Frontier Airlines announced Monday morning that passengers will have to pay extra to place carry-on luggage in the overhead bin and for advanced seating assignments. The new stripped-down cost structure will cut the average price of an economy ticket by nearly 12 percent, according to airline officials.

Frontier Airlines previously added a $1.99 surcharge for soda or water last July and is currently one of three U.S. carriers—alongside Spirit Airlines and Allegiant Air—to charge such fees. The new charges apply to tickets purchased on or after Monday.

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Frontier carries 8.4 million passengers a year, about 1 percent of the overall traffic flown by U.S. airlines, reports the Associated Press. Currently, there is no indication that larger carriers like American Airlines, Delta Air Lines, Southwest Airlines or United Airlines are considering similar fees.

Optional Service fees are listed on Frontier’s website. It says the average fee for using the overhead bin ranges from $20 for frequent fliers who book online to $50 for those who pay at the gate. The most common fee is $25 for online check-in and $35 for airport check-in. Personal items that can fit under the seat are free.

Frontier previously charged only those customers who booked tickets through third-party sites like Expedia and Orbitz.

Additionally, seat assignments—even for the dreaded middle seat—now cost an extra $3 for those who buy while booking online and an extra $8 at check-in. If passengers don’t pay extra, Frontier will assign them whatever seats are left over.

Frontier will also follow other airlines in charging extra for seats with more legroom or those closer to the front of the plane. The front half of the plane, according to Frontier’s website, will cost customers an extra $5 to $15 per flight. Seats with an extra 5 to 7 inches of legroom will also cost more, ranging from $15 to $50 per flight. Connecting passengers would have to pay these fees twice.

Boston passengers flying Spirit Airlines at Logan Airport should check their fees before booking. According to their website, Spirit charges an additional fee for carry-on luggage, starting at $26 for online check-in and going up to $100 for those who pay at the gate. Seat reservations cost around $50 for “average” seats and up to $150 for wider seats with legroom and other features. Snacks and drinks will also cost passengers between $5 and $15 per item.

Frontier’s president, Barry L. Biffle, told the Associated Press that they modeled their new fee system after Spirit.